Mammoth Uncensored Word List:
98 - 10 letter words starting with is

isabelline isallobars ischaemias ischuretic iseikonias isentropic islomanias isoaminile isoantigen isobarisms isobutanes isobutenes isobutynes isocaloric isochasmic isocheimal isocheimic isochimals isochronal isochrones isochronic isochroous isoclinals isoclinics isocracies isocrymals isocyanate isocyanide isodecanes isodecenes isodecynes isodontals isodynamic isoenzymes isoenzymic isoflavone isogametes isogametic isogenetic isoglossal isoglosses isoglossic isoglottal isoglottic isografted isoheptane isoheptene isoheptyne isohexanes isohexenes isohexynes isohyetals isokinetic isokontans isolatable isolations isoleucine isomerases isomerised isomerises isomerisms isomerized isomerizes isometrics isometries isomorphic isoniazide isoniazids isonitrile isononanes isononenes isononynes isooctanes isooctenes isooctynes isopachyte isopentane isopentene isopentyne isopiestic isoplethic isoprenoid isopropyls isopterous isopycnals isopycnics isoseismal isoseismic isospories isosporous isostacies isostasies isotherals isothermal isotropies isotropism isotropous ispaghulas